1. Field of the Invention
The present invention relates to a horizontal multi-link type robot in which a plurality of arms are connected together and to a support shaft capable of moving up and down such that the arms can revolve around vertical lines.
2. Discussion of the Background
In a conventional horizontal multi-link type robot where arms rotate about vertical lines, a first arm which is rotatable about a vertical line is mounted to the upper end of a translation portion which moves up and down relative to the base. A second arm is mounted rotatable about an axis parallel to the vertical line about which the first arm rotates.
Generally, in horizontal multi-link type robots of this kind, the servomotor for rotating the second arm has been mounted so as to protrude from an upper portion of the first arm in coaxial relation to the axis about which the first arm rotates, while the servomotor for rotating the first arm has been mounted to an upper portion of the outer surface of the translation portion on the opposite side to the second arm. Accordingly, the robot of this construction requires a large space for installation.
In an attempt to solve the aforementioned problem, the servomotor for rotating the second arm has been mounted to a lower position on the first arm, and the second arm has been mounted rotatable about the shaft to which the first arm is held. In this construction, however, the first and second arms and the servomotor for the second arm are all held to the shaft on the side of the second arm, and therefore the moment about the shaft to which the first arm is held is greatly imbalanced. The result is that a greater load is imposed on the servomotor for the first arm. Further, since the servomotor for the first arm is mounted to an upper position on the outer surface of the translation portion on the opposite side from the second arm, it is technically impossible to mount the servomotor for the first arm to a lower position on the first arm and on the opposite side of the first arm support shaft from the second arm.